History Matching of the Last Glacial Cycle Model for the Icelandic and Patagonian Ice Sheets

To date, the Icelandic Ice Sheet (IIS) and Patagonian Ice Sheet (PIS) have been poorly understood with regard to their configuration, dynamics, and evolution during the last glacial cycle. The few glaciological modelling studies of the IIS and PIS to date have placed minimal attention on addressing model uncertainties. As such, their inferential value is poorly interpretable.

To address this, we present the results of history matchings of the 3D Glacial Systems Model (GSM) against curated sets of paleo constraints for the last glacial cycle IIS and PIS. History matching identifies a set of model simulations that are not ruled out given available data constraints and robust uncertainty analysis (including both model and data uncertainties). As such, it aims to “bracket reality” as opposed to the much more difficult task of determining a meaningful most likely chronology.

The GSM is a thermo-mechanically coupled glaciological model with hybrid shallow ice and shallow shelf/stream physics. The climate forcing consists of a fully coupled energy balance climate model and glacial indexed climate forcing using the results of PMIP3 (Paleo Model Intercomparison Project). Approximate 30 GSM ensemble parameters partially account for uncertainties in climate, basal drag, and marine ice processes. The GSM configuration includes fully coupled visco-elastic glacio-isostatic adjustment enabling physically self-consistent relative sealevel predictions. Our presentation focuses on bracketing chronologies for the last glacial cycle IIS and PIS as well as disentangling the relative contribution of atmospheric and marine forcings on mass loss during the deglaciation.